The present invention relates to arthroplastic reconstruction of the human joints and more particularly to implant arthroplasty of the wrist joint
In recent years, various implants have been successfully employed for the restoration of the joints of the hand and wrist affected with rheumatoid arthritis and similar conditions. Aseptic necrosis and/or arthritis of the carpal bones, either primary or secondary to trauma, is a frequent cause of disability of the wrist. Surgical treatment of conditions of the wrist have included intercarpal fusion, wrist fusion, local resection, proximal row carpectomy, bone grafting, radial styloidectomy, radial shortening or ulnar lengthening and soft tissue interposition arthroplasty.
Rheumatoid arthritis may affect the soft tissues and the joints of the wrist, including the radiocarpal, intercarpal and radioulnar joints. The disease may result in loosening of the ligaments and erosive changes in the bones. This disturbs the multiple link system of the wrist joint. In severe cases, the wrist may become completely dislocated. Ulnar displacement of the proximal carpal row may result from loosening of the ligaments on the radial aspect of the joint. Radial deviation of the hand on the forearm may then result. Subluxation of the distal radioulnar joint associated with such deviation causes a loss of stability on the ulnar aspect of the wrist.
Wrist implant arthroplasty has been employed when instability of the wrist is caused by subluxation or dislocation of the radiocarpal joint. A double stem implant has been used with one stem inserted into the intramedullary canal of the radius and the other stem inserted in a channel reamed through the remnant of the capitate bone and the third metacarpal. In addition, an intramedullary stemmed, cuffed implant may be used to cap the resected distal ulna to preserve the anatomic relationships and physiology of the distal radioulnar joint following ulnar head resection.
The aforementioned U.S. Pat. No. 4,645,505 overcomes many problems heretofore experienced with wrist implant arthroplasty. The implant disclosed therein defines a recess dimensioned to receive a portion of the carpal row and prevent ulnar migration of the row and wrist dislocation. The implant has a dorsal sidewall and a palmar sidewall and is symmetrical about a longitudinal centerline. The implant locks the lunate and prevents ulnar migration of the carpal tunnel row. The implant, however, shifts extension and flexion movements to the midcarpal joint. While reducing pain and stabilizing the wrist, movement is limited.
A need exists for an implant for the wrist which stabilizes the radiocarpal joint and proximal carpal row but which does not shift movement to the midcarpal joint.